Hierarchical Approach for Solvent Selection in Circular Economy

Chemical recycling allows upcycling of polymers into their monomers and/or other valuable chemicals and contributes to a resource-efficient future. This demands selective depolymerization of a particular fraction from a mixed waste stream and thereby, necessitates the use of appropriate solvents. The solvent not only governs the effective depolymerization of the polymer but also influences the sustainability of the process. Conventionally, the tendency of the solvent to dissolve the polymer is considered as the only selection criterion. However, careful consideration should also be given to its interaction with other process reagents and its sustainability. This research proposes a systematic approach to identify potential solvents suitable for a particular recycling strategy. The hierarchical approach begins with identifying potential solvents using computer-aided molecular design based on the Hansen Solubility Parameters (HSPs) of the target polymer. Further, their interactions with other process reagents are also considered. Subsequently, they are screened for their sustainability through a comprehensive life-cycle assessment and some short-listed systems are further evaluated using process simulation. The application of this methodology for developing a recycling strategy for PLA is illustrated.